With pre-production of The Hobbit now well underway and filming planned for early 2010, casting rumours are starting to circulate in earnest. Sir Ian McKellen recently claimed to be the only returning castmember from the trilogy, but Andy Serkis and Hugo Weaving had both previously indicated they should be returning as Gollum and Elrond, respectively.
The casting of Bilbo Baggins is currently the biggest question over the topic, with Daniel Radcliffe ruling himself out due to fantasy burn-out. Soon-to-be-former Doctor Who star David Tennant has been heavily rumoured, but current favourite is probably Scottish actor James McAvoy (who also gets Radcliffe's backing).
A new name has now entered the ring, with the Latino Review claiming that Spider-Man star Tobey Maguire might be a contender. According to their sources, Maguire is in talks with the film's producers. Apparently he is very keen to work with director Guillermo Del Toro on a project.
What is likely to be a key consideration over whether this happens or not is timing. Spider-Man 4 begins shooting in March 2010, which is tight given that The Hobbit's start date (not set in stone yet) has been mooted for between April and June 2010. It's possible that Maguire's involvement could be a good reason for a later start date to be picked, and indeed just recently there was some talk about filming being held back to the summer, so this could all come together nicely.
The Hobbit is currently planned to film for a year and should be released in two parts, with the first part being released in December 2011 on the tenth anniversary of The Fellowship of the Ring.